Saudi Arabia's execution of a leading Shiite cleric reflects an assertive but risky new approach that threatens to escalate its proxy wars with arch-rival Iran in Syria and Yemen, experts said Sunday.
Hours after the Sunni-ruled kingdom announced Saturday's execution of Sheikh Nimr al-Nimr, a driving force behind anti-government protests in 2011, angry demonstrators set fire to its embassy in Shiite-dominated Iran.
In response, Saudi Foreign Minister Adel al-Jubeir announced Sunday that Riyadh was severing diplomatic ties with Tehran and said all Iranian diplomats must leave the kingdom within 48 hours.
The United States said Nimr's execution "risks exacerbating sectarian tension", while the European Union warned of "dangerous consequences" across the volatile region.
Nimr had been on death row since 2014, but his execution, rather than leaving him behind bars indefinitely, was still surprising given the likelihood it would further enflame Sunni-Shiite tensions.
"Iran betted in the past on a hesitant foreign and domestic Saudi policy, but over the past year, things have completely changed and Riyadh has assumed a position that is rather provocative towards Tehran," said Mahjoob al-Zweiri, professor of Middle Eastern studies at Qatar University.
Nearly a year ago, King Salman succeeded his half brother Abdullah as the monarch of the region's Sunni heavyweight.
He brought along his nephew Mohammed bin Nayef as crown prince and interior minister and his own young and ambitious son Mohammed as a deputy crown prince and defence minister.
In March, Saudi Arabia took the unforeseen step of leading an Arab military intervention in neighbouring Yemen, launching an air campaign against Iran-backed Shiite Huthi rebels in support of President Abedrabbo Mansour Hadi.
- 'Element of rationality' -
Last month, Riyadh brought Syrian political and armed opposition factions together for unprecedented talks, reflecting its rising profile in efforts to end the war.
Shortly after -- and completely unexpectedly -- Defence Minister Prince Mohammed announced the formation of a 34-nation coalition against Islamic "terrorism".
"Riyadh presses ahead with its actions without giving much thought to reactions," said Zweiri.
"It seems that there is a belief now that proactive and determined policies by Saudi Arabia could achieve results, including responding to Iran and its policies in the region," he said.
But for Francois Heisbourg, an adviser at the Paris-based Foundation for Strategic Research, Nimr's execution is part of Saudi Arabia's "headlong rush combined with an element of rationality".
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If the Saudis "think that the confrontation with Iran is inevitable, they might as well provoke it now when (their allies) the Americans are still around and that Iran is still in a relatively weak economic and military state," he said.
Nimr, 56, was executed along with 46 other men, mostly Sunnis accused of involvement in Al-Qaeda killings, according to the interior ministry.
Iran warned of a "high price" that Saudi Arabia will pay, but the Saudis shrugged off Tehran's reaction as "irresponsible".
"We are completely confident with what we're doing and we believe in it and do not care how others view our procedures, whether on justice or implementation of sentences," said interior ministry spokesman Mansur al-Turki.
- 'Polarisation' -
Jane Kinninmont, of the Chatham House think tank in London, said the execution "reflects a hard line on internal criticism and is not simply a reflection of regional politics" as Nimr was a "vocal and passionate critic of the royal family".
Speaking before Riyadh broke off diplomatic ties with Tehran, she said she expected that Nimr's execution would "add to Saudi-Iranian polarisation".
"Iran is increasingly seeking to position itself as the defender of Shiite interests globally, and has a growing constituency as many Shiites feel beleaguered and victimised, especially with the rise of ISIS," she said, referring to the Islamic State group.
"Saudi authorities will see the Iranian response as an apparent validation of their perception that Iran is meddling in their domestic affairs."
Zweiri said he expected tensions over the execution to have far-reaching consequences.
"This tension might push Tehran towards more coordination with Russia to complicate the situation further in Syria," he said of Moscow's military intervention in support of President Bashar al-Assad.
Tehran "might also aim to prolong the conflict in Yemen where it would aim to exhaust Saudi Arabia, particularly with the sharp drop in oil prices," he said.
"The difference between Riyadh and Tehran concerning oil prices is that Tehran sees itself trained to face such tough conditions, like with the sanctions, while Riyadh is not."
Zweiri added, however, that the kingdom's decision to lead major Gulf oil exporters in rejecting a production cut despite plummeting oil revenues is part of Riyadh's pressure on Tehran.
"This is also linked to the kingdom's oil policy that Iran sees similar to a declaration of war targeting any attempt to revive the Iranian economy after the easing of sanctions" by the international community.